Heating system for regenerative coke ovens

ABSTRACT

According to the invention the heating system for regenerative coke oven batteries that can be heated with rich gas and/or lean gas or mixed gas is provided comprising vertical flues cooperating in pairs, each vertical flue being connected to a regenerator for preheating the air and, in the case of lean gas operation, for preheating the lean gas or mixed gas. High and low combustion stages, as well as structure defining an internal flue gas return at levels above a flue base are provided. Discharge openings are provided at at least three levels for supplying each flue. A base discharge opening is provided at the flue base directly connected to regenerators. Hollow communicating channels are defined for connecting the regenerators to discharge openings located above the flue base. The hollow communicating channels are preferably formed in each communicating wall connected to a discharge opening leading only to one adjacent flue. The regenerators for preheating air are subdivided in a longitudinal direction of the oven with one part being connected to the base openings at the flue base and another part being connected to the hollow communicating channels. A regulating system is provided for setting the amount of air for the two parts separately. Pressure blocks are provided for setting the air distribution at the discharge openings provided above the flue base. The circulating flow openings are arranged at the foot of each flue in a hollow communicating wall between adjacent flues to provide ascending and descending flow.

FIELD OF THE INVENTION

The present invention pertains to a heating system for regenerative cokeoven batteries that can be heated with rich gas and/or lean gas or mixedgas, with vertical flues cooperating in pairs, the flues beingconnectable to regenerators for preheating the air and, in the case oflean gas operation, also connectable with regenerators for preheatingthe lean gas or mixed gas, high and low combustion stages, as well aswith an internal flue gas return at levels of the flue base.

BACKGROUND OF THE INVENTION

A heating system with flues cooperating in pairs, air supply stageslocated high and low, as well as a flue gas return at the level of theflue base, has been known from European Patent Application No.0,183,908. In these only two air supply stages over the height of theflue, the supply of air and gas at the base of each flue forms the firststage, and the supply via hollow communicating channels and dischargeslots, located at the same height for both adjacent flues, forms thesecond stage. Heating with only two air supply stages is not sufficientfor optimal combustion and for minimizing the NO_(x) formation in cokeovens with a chamber height exceeding, e.g., 4 m.

SUMMARY AND OBJECTS OF THE INVENTION

The primary object of the heating system according to the presentinvention is to achieve uniform heating of the oven chambers with thesmallest possible amount of NO_(x) formation even in the case of agreater oven height, wherein optimal control of each individualcombustion stage is possible even during ongoing operation, especiallyafter a change from one type of gas to another.

This new heating system is characterized especially by the fact that theamount of the combustion air supplied at three or more levels can beadjusted from the outside for each individual stage even during ongoingoperation. The three-stage or more than three-stage air supply permitsboth multistage combustion or heating of the oven chambers over theheight and--to reduce the nitrogen oxide formation--alsosubstoichiometric combustion in the lower combustion zones of the flue,as well as lower flame temperatures. At the same time, a furtherpossibility for reducing the nitrogen oxide emission is fully utilizedvia flue gas return, besides the stepwise admission of the combustionair.

Besides the internal return with the so-called circulating flowopenings, the return of relatively cold flue gases from the smokestackcanal and mixing it with the combustion air is suggested according tothe present invention as an external flue gas return. Especially thereturned flue gas can be mixed with the combustion air and heated to thepreheating temperature in the regenerators.

To achieve optimal combustion control in the ascending flues, it issuggested according to the present invention that the rich gas nozzlesto which gas is admitted during one heating period be arranged in thelongitudinal direction of the oven in one plane in the vicinity of onetraveling wall in front of the corresponding circulating flow openings,and the rich gas nozzles to which gas is admitted during the otherheating phase be also arranged in the longitudinal direction of the ovenin one plane in the vicinity of the other traveling wall in front of thecorresponding circulating flow openings.

It was also found to be favorable to arrange only one discharge opening,which is connected to a regenerator carrying lean gas or mixed gas, atthe flue base in each flue, to supply the weak gas or mixed gas intoeach flue. In view of the fact that this gas usually burns with a longerflame, sufficient heating of the oven charge can be achieved with thisexclusive gas supply at the flue base even in the case of tallerchambers. The discharge openings at the flue base for both the air andoptionally for the lean gas or mixed gas are preferably arranged exactlyin the middle of the flue between the two corresponding traveling walls.

As an advantageous embodiment, it is suggested for a heating system of atwin flue type that a hollow communicating channel with dischargeopenings leading only to one adjacent flue be arranged in eachcommunicating wall. The circulating flow openings should be arrangedaccording to the present invention in the communicating walls which arelocated between ascending and descending flues of one twin flue group.

To set the amount of the combustion media over the length of theregenerators, adjustable and/or interchangeable regulating plates arearranged under these and above the regenerator base channels. Inaddition, the individual regenerators are subdivided by cell wallsextending in the longitudinal direction of the battery into sectionswhich are connected to a flue each in the two adjacent heating walls. Asa result, each twin flue with the regenerator section associated with itforms one heating unit, so that the supply of combustion air and leangas or mixed gas to each individual heating unit can be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a vertical sectional view taken in the longitudinal directionof the heating wall through part of a heating wall with two adjacenttwin flue groups,

FIG. 1a is a cross sectional view taken along line 1a--1a of FIG. 1.

FIG. 2 is a vertical sectional view taken in the longitudinal directionof the battery through some heating walls with associated oven chambersand regenerators.

FIG. 3 is a horizontal sectional of view taken through a part of aheating wall, and

FIG. 4 is a horizontal sectional of view taken through a part of aplurality of heating walls arranged next to one another withschematically indicated, associated regenerators and the supply channelsto the heating walls.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The figures show a so-called compound oven, which can be optionallyheated with rich gas G or lean gas G or mixed gas G. For exclusive richgas operation, the rich gas G is supplied to the ascending flues 3alternatingly via the rich gas nozzles 8 or 9. The combustion air A isalso fed into the ascending flues via the regenerator base channels 12,the regulating plates 13, the regenerators 14, 15, 16, and the dischargeopenings 5 through 7. The air A thus enters the flue base from theregenerator 14 via the discharge openings 7; the air A from theregenerator 15 reaches the flue base via the discharge opening 6; andthe air A from the regenerator 16 enters the ascending flue 3 via thehollow communicating channels 4 and the two upper discharge openings 5between two opposite side walls or traveling walls 2.

Two adjacent ascending and descending flues 3, 3a are integrated intoone twin flue from the viewpoint of heating, and one of these flues(ascending flue) is exposed to the flame alternatingly, the other fluedischarges the flue gases W (exhausting flue).

In the case of lean gas heating, a lean gas G or a mixed gas G fromblast-furnace gas and coke oven gas is preheated in the regenerators 14,and fed to the flue base via the discharge opening 7. To supply thecombustion air A, at least three openings are provided at differentlevels in each flue: one discharge opening 6 is located in the flue baseand two or more discharge openings 5 are located at a communicating wall20, 21 at different heights. To make it possible to adjust thecombustion air, supply A, in the individual stages to the requirementsof the operation, especially in the case of change from one type of gasto another, the air regenerators 15, 16 are connected to the flue by oneof separate base channels and, the communicating channels 4 formed in aguide wall. One regenerator side 15 supplies the bottom outlets 6 in theflue with combustion air, and the other regenerator 16 supplies theupper communicating wall discharge openings 5. The admission of gas tothe discharge openings (bottom outlets) 6 at the flue base, on one hand,and to the upper discharge openings 5, on the other hand, can thus beset outside the oven, and changed over in the case of a change from onetype of gas to another.

The waste gases W generated in the ascending flues 3 pass over into theadjacent descending flue 3a through openings in the upper part of thecommunicating walls, and are removed via the openings 5 and the hollowcommunicating channels 4a, as well as the bottom openings 6, 7 of thisflue, the corresponding regenerators 14, 15 16, and the base channels12.

Waste gas W flows through all metering cross sections for lean gas G orcombustion A air after changing over the heating. This leads to ananalogous distribution among the regenerators for this medium. Theseregenerators are thus again heated uniformly, and the waste gases W arecooled uniformly. Should it become necessary to change the amounts ofcombustion air A between the two upper discharge openings 5, this can bedone by changing the discharge openings e.g., by means of pusher blocks17, cf. FIG. 1a.

As further measures in addition to the stepwise supply of the combustionair A, internal and external returns of flue gas W are provided in orderto minimize the formation of nitrogen oxides. For the internal flue gasW return, two so-called circulating flow openings 18, 19 are provided inthe lower part of every other communicating wall 21. Even thoughbuoyancy occurs in both flues, it is greater in the ascending flue 3.Thus a pressure, gradient develops at the foot of the flues, so thatflue gases W will flow over there from the descending flue 3a into theascending flue 3.

To achieve the greatest possible effect in terms of the reduction of theamount of nitrogen oxides formed with the internal flue gas return, therich gas nozzles 8, 9 are arranged in front of respective circulatingflow openings 18, 19, so that the coke oven gas can be enveloped ormixed with returned waste gas W beneath the actual combustion zone. Ifneeded, the circulating flow openings 18, 19 can be closed by means ofadjusting rollers 10, 11 provided on the flue base.

For external flue gas return, relatively cold flue gases W are returnedfrom the smokestack canal, and they are mixed with the combustion air A,as a result of which the flue gases W mixed in are also heated in theregenerators to the preheating temperature, which is slightly below theflue temperature. The flue gases W are returned by means of blowers, andthe waste gases W are taken from one of the smokestack canals of twoadjacent batteries via reversible lines.

Since no waste gases W are produced during the periodic heatingchangeover of the battery, exhaust is first switched over to thesmokestack canal of the respective other battery. The waste gases W aresubsequently mixed with the combustion air A, which is also drawn in bymeans of blowers for this reason and is fed via lines or channels to thebatteries. The forced circulation of the returned waste gases W with thecombustion air A makes it additionally possible to use filtered leakagegases drawn in above the coke oven doors as combustion air A. Bysupplying the combustion air A under pressure via lines and stopcocks,advantages in terms of the possibility of accurate control of the totalamount and of metering of the individual streams can be expected.

On the whole, among other things, the possibility of accuratelycontrolling the amount of air makes it possible to accurately controlthe temperature program in the flues and to accurately set the airexcess coefficient at the individual combustion stages, as a result ofwhich the amount of nitrogen oxide produced can be expected to bereduced.

FIG. 1 additionally shows the alternating arrangement of continuouscommunicating walls 20, which separate two twin flue groups from oneanother, and short communicating walls 21. A differential channel 22, towhich gas can be admitted on opening of the pushers 24 to additionallyheat a higher oven zone, is located above a twin flue group. A peephole23 is located above each flue, among other things, in order to monitorthe temperatures in the flues and to adjust the pusher blocks 17 and theadjusting rollers 10, 11.

The regenerator cell walls 25 drawn in broken lines in FIG. 4 shouldalso be mentioned.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

We claim:
 1. A heating system for regenerative coke oven batteries thatcan be heated with rich gas and/or lean gas or mixed gas, comprising;abase wall, an upper wall and side walls defining at least onecooperating pair of vertical flues, said sidewalls including a shortcommunicating wall dividing said cooperating pair of vertical flues andextending from said base wall to a location spaced from said upper walland a continuous communicating wall extending from said base wall tosaid upper wall, each of said short communicating wall and saidcontinuous communicating wall defining a hollow communicating channel,each said hollow communicating channel including discharge openings attwo different levels above said base wall, said discharge openings ofsaid continuous communicating wall leading only to a first flue of saidcooperating pair of vertical flues and said discharge openings of saidshort communicating wall leading only to a second flue of saidcooperating pair of vertical flues; flue base communicating channelmeans formed in said flue base wall defining a channel with a flue basedischarge opening connected to said first flue, regenerators forpreheating air, said regenerators being subdivided in a longitudinaldirection of said heating system to provide a first regenerator partwith a first regenerator part connection and a second regenerator partwith a second regenerator part connection, said first regenerator partconnection being connected to said flue base communicating channel meansand said second regenerator part connection being connected to saidhollow communicating channel of said continuous communicating wall,allowing adjustment of amounts of air therebetween; pusher block meansprovided at each of said discharge openings of said one of said hollowcommunicating channels for regulating gas flow therethrough; and a baseopening provided in said short communicating wall between thecooperating pair of vertical flues for providing communication betweensaid second flue and said first flue adjacent said base wall.
 2. Aheating system according to claim 1, further comprising a first heatingperiod rich gas nozzle providing a rich gas connection to one flue ofsaid pair of cooperating flues said first heating period rich gas nozzleconnection being in front of said base opening and a second heatingperiod rich gas nozzle providing a rich gas connection to the other flueof said pair of cooperating flues, said second heating period rich gasnozzle connection being in front of said base opening.
 3. A heatingsystem according to claim 1, wherein said flue base communicatingchannel means defines an additional discharge opening connected to anadditional regenerator for supplying lean gas or mixed gas.
 4. A heatingsystem according to claim 3, wherein said base discharge opening andsaid additional discharge opening are arranged between said continuouscommunicating wall and said short communicating wall.
 5. A heatingsystem according to claim 1, further comprising regenerator basechannels connected to said first and second regenerator parts andregulating plates arranged under said first and second regenerator partsand above said regenerator base channels.
 6. A heating system accordingto claim 1, wherein each of said first regenerator part and said secondregenerator part includes a cell wall to divide said first regeneratorpart and to divide said second regenerator part.